Antistatic strenique polymer compositions

ABSTRACT

The invention relates to a composition comprising, for 100 parts by weight, 99-60 parts of a styrenic polymer (A), 1-40 parts of (B)+(C), (B) being a polyamide block and polyether block copolymer essentially comprising ethylene oxide patterns (C2H4-O)—, (C) being a compatibilizer of styrene and at least one polymerized block comprising ethylene patterns, (B)/(C) ranging from 2 to 10.

The present invention relates to antistatic styrenic polymercompositions and more specifically to a composition comprising astyrenic polymer (A), a copolymer (B) containing polyamide blocks andpolyether blocks comprising essentially ethylene oxide units —(C₂H₄—O)—,and a compatibilizer (C).

The aim of the invention is to give the styrenic polymer (A) antistaticproperties. The formation and retention of static-electricity charges onthe surface of most plastics are known. The presence of staticelectricity on thermoplastic films results, for example, in these filmssticking to one another, making them difficult to separate. The presenceof static electricity on packaging films may cause the accumulation ofdust on the articles to be packaged and thus impede their use. Styrenicresins, such as polystyrene or ABS, are used to make cases forcomputers, for telephones, for televisions, for photocopiers, and fornumerous other articles. Static electricity causes accumulation of dustbut most importantly can also cause damage to microprocessors orconstituents of electronic circuits present in these articles. For theseapplications, it is generally desirable to find compositions based onstyrenic resin whose surface resistivity is below 5.10¹³ ?/? measured tothe standard IEC93 or whose volume resistivity is below 5.10¹⁶ ?.cmmeasured to the standard IEC93 (the type of resistivity being chosen asa function of the application, given that these two types of resistivityalways increase in the same direction). This is based on theconsideration that these resistivities provide adequate antistaticproperties for certain applications in the field of polymer materials incontact with electronic components.

The prior art has described antistatic agents, such as ionic surfactantsof ethoxylated amine type or sulfonate type which are added withinpolymers. However, the antistatic properties of the polymers depend onambient humidity and are not permanent, since these agents migrate tothe surface of the polymers and disappear. Copolymers containinghydrophilic polyether blocks and polyamide blocks have therefore beenproposed as antistatic agents, these agents having the advantage of notmigrating and therefore of providing antistatic properties which arepermanent and less dependent on ambient humidity.

The Japanese patent application JP 60 170 646 A, published Sep. 4, 1985,describes compositions consisting of from 0.01 to 50 parts of polyetherblock amide and 100 parts of polystyrene, these being used to makesliding parts and wear-resistant parts. The antistatic properties arenot mentioned.

Patent application EP 167 824, published Jan. 15, 1986, describescompositions similar to the preceding compositions, and according to oneembodiment of the invention the polystyrene may be blended with apolystyrene functionalized by an unsaturated carboxylic anhydride. Thesecompositions are used to make injection-molded parts. The antistaticproperties are not mentioned.

The Japanese patent application JP 60 023 435 A, published Feb. 6, 1985,describes antistatic compositions comprising from 5 to 80% ofpolyetheresteramides and from 95 to 20% of a thermoplastic resin chosenfrom, inter alia, polystyrene, ABS and PMMA, this resin beingfunctionalized by acrylic acid or maleic anhydride. The amount ofpolyetheresteramide in the examples is 30% by weight of thecompositions.

The patent EP 242 158 describes antistatic compositions comprising from1 to 40% of polyetheresteramide and from 99 to 60% of a thermoplasticresin chosen from styrenic resins, PPO and polycarbonate. According to apreferred embodiment, the compositions also comprise a vinyl polymerfunctionalized by a carboxylic acid, one example being a polystyrenemodified by methacrylic acid.

The international patent application PCT/FR00/02140 teaches the use ofcopolymers of styrene and of an unsaturated carboxylic anhydride,copolymers of ethylene and of an unsaturated carboxylic anhydride,copolymers of ethylene and of an unsaturated epoxide, block copolymersin the form of SBS or SIS grafted with a carboxylic acid or anunsaturated carboxylic anhydride, as compatibilizer between a styrenicresin and a copolymer containing polyamide blocks and polyether blocks.

Other prior-art documents which may be cited are:

-   -   EP 927727,    -   J. Polym. Sci., Part C: Polym. Lett. (1989), 27(12), 481    -   J. Polym. Sci., Part B, Polym. Phys. (1996), 34(7), 1289    -   JAPS, (1995), 58(4), 753    -   JP 04370156    -   JP 04239045    -   JP 02014232    -   JP 11060855    -   JP 11060856    -   JP 09249780    -   JP 08239530    -   JP 08143780

The prior art demonstrates either blends (i) of styrenic resin andpolyetheresteramide without compatibilizer or blends (ii) ofpolyetheresteramide and functionalized styrenic resin or else blends(iii) of polyetheresteramide, non-functionalized styrenic resin andfunctionalized styrenic resin.

The blends (i) are antistatic if the polyetherester-amide is carefullychosen, but have poor mechanical properties, elongation at break inparticular being much lower than that of the styrenic resin alone. Asfar as the blends (ii) and (iii) are concerned, it is necessary to haveaccess to a functionalized styrenic resin, and this is a complicated andcostly matter. The object of the invention is to provide antistaticproperties to the ordinary styrenic resins used to make theabovementioned articles, these being non-functionalized resins. It hasnow been found that when particular compatibilizers are used it ispossible to obtain styrenic resin compositions which comprise a styrenicresin and a copolymer containing polyamide blocks and polyether blocks,and which have excellent elongation at break, excellent tensile strengthand excellent impact resistance (Charpy notched), when compared with thesame composition without compatibilizer.

The present invention provides a

-   composition comprising per 100 parts by weight:    -   from 99 to 60 parts by weight of a styrenic polymer (A),    -   from 1 to 40 parts by weight of (B)+(C),-   (B) being a copolymer containing polyamide blocks and polyether    blocks comprising essentially ethylene oxide units —(C₂H₄—O)—,    and (C) being a compatibilizer chosen from block copolymers    comprising at least one polymerized block comprising styrene and at    least one polymerized block comprising ethylene oxide units.

In the polymerized block comprising ethylene oxide units, the repeatunit is —O—CH₂—CH₂—. This block may also be called a PEG (i.e.polyethylene glycol) block.

Polyphenylene oxide (PPO) may be absent in the composition according tothe invention.

By way of example of styrenic polymer (A) mention may be made ofpolystyrene, polystyrene modified by elastomers, random or blockcopolymers of styrene and of dienes such as butadiene, copolymers ofstyrene and of acrylonitrile (SAN), SAN modified by elastomers, inparticular ABS, obtained, for example, by grafting (graftpolymerization) of styrene and acrylonitrile on a graft-base composed ofpolybutadiene or of butadiene-acrylonitrile copolymer, and blends of SANand of ABS. The abovementioned elastomers may be, for example, EPR(abbreviation for ethylene-propylene rubber or ethylene-propyleneelastomer), EPDM (abbreviation for ethylene-propylene-diene rubber orethylene-propylene-diene elastomer), polybutadiene,acrylonitrile-butadiene copolymer, polyisoprene, isoprene-acrylonitrilecopolymer. In particular, A may be an impact polystyrene comprising amatrix of polystyrene surrounding rubber nodules generally comprisingpolybutadiene.

In the abovementioned polymers (A), part of the styrene may be replacedby unsaturated monomers copolymerizable with styrene, and by way ofexample mention may be made of alpha-methylstyrene and the (meth)acrylicesters. In this case, A may comprise a copolymer of styrene, among whichmention may be made of styrene-alpha-methyl-styrene copolymers,styrene-chlorostyrene copolymers, styrene-propylene copolymers,styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-vinylchloride copolymers, styrene-vinyl acetate copolymers, styrene-alkylacrylate copolymers (methyl acrylate, ethyl acrylate, butyl acrylate,octyl acrylate, phenyl acrylate), styrene-alkyl methacrylate copolymers(methyl methacrylate, ethyl methacrylate, butyl methacrylate, phenylmethacrylate), styrene-methyl chloroacrylate copolymers andstyrene-acrylonitrile-alkyl acrylate copolymers. The content ofcomonomers in these polymers is generally up to 20% by weight. Thepresent invention also provides high-melting-point metallocenepolystyrenes.

Without exceeding the scope of the invention, (A) could be a blend oftwo or more of the preceding polymers.

The styrenic polymer A preferably comprises more than 50% by weight ofstyrene. If the styrenic polymer is SAN, it preferably contains morethan 75% by weight of styrene.

The polymers (B) containing polyamide blocks and polyether blocks arethe result of copolycondensation of terminally reactive polyamidesequences with terminally reactive polyether sequences, examples being,inter alia:

-   1) Polyamide sequences having diamine chain ends with    polyoxyalkylene sequences having dicarboxylic chain ends.-   2) Polyamide sequences having dicarboxylic chain ends with    polyoxyalkylene sequences having diamine chain ends and obtained via    cyanoethylation and hydrogenation of alpha-omega-dihydroxylated    aliphatic polyoxyalkylene sequences known as polyetherdiols.-   3) Polyamide sequences having dicarboxylic chain ends with    polyetherdiols, the products obtained in this particular case being    polyetheresteramides. The copolymers (B) are advantageously of this    type.

The polyamide sequences having dicarboxylic chain ends derive, forexample, from the condensation of alpha-omega-aminocarboxylic acids, oflactams or of dicarboxylic acids and diamines in the presence of adicarboxylic acid as chain regulator.

The number-average molecular weight {overscore (Mn)} of the polyamidesequences is between 300 and 15 000 and preferably between 600 and 5000.The weight {overscore (Mn)} of the polyether sequences is between 100and 6000 and preferably between 200 and 3000.

The polymers containing polyamide blocks and polyether blocks may alsocomprise units having random distribution. These polymers may beprepared via simultaneous reaction of the polyether and of theprecursors of the polyamide blocks.

For example, a reaction may be carried out using polyetherdiol, a lactam(or an alpha-omega-amino acid) and a diacid chain regulator in thepresence of a little water. This gives a polymer having essentiallypolyether blocks and polyamide blocks of very variable length, and alsohaving the various reactants randomly distributed along the polymerchain, having reacted in random fashion.

These polymers containing polyamide blocks and polyether blocks whichderive from the copolycondensation of polyamide sequences and polyethersprepared previously or from a one-step reaction have, for example, ShoreD hardnesses which can be between 20 and 75 and advantageously between30 and 70 and have intrinsic viscosity between 0.8 and 2.5 measured inmeta-cresol at 250° C. for an initial concentration of 0.8 g/100 ml. TheMFIs may be between 5 and 50 (235° C. under a load of 1 kg).

The polyetherdiol blocks are either used as they stand andcopolycondensed with the carboxylic-terminated polyamide blocks or areaminated and then converted to polyetherdiamines and condensed with thecarboxylic-terminated polyamide blocks. They may also be mixed withprecursors of polyamide and a chain regulator to make polymerscontaining polyamide blocks and polyether blocks having randomlydistributed units.

Polymers containing polyamide blocks and polyether blocks are describedin the patents U.S. Pat. No. 4,331,786, U.S. Pat. No. 4,115,475, U.S.Pat. No. 4,195,015, U.S. Pat. No. 4,839,441, U.S. Pat. No. 4,864,014,U.S. Pat. No. 4,230,838 and U.S. Pat. No. 4,332,920.

In a first embodiment of the invention, the polyamide sequences havingdicarboxylic chain ends derive, for example, from the condensation ofalpha-omega-amino-carboxylic acids, of lactams or of dicarboxylic acidsand diamines in the presence of a dicarboxylic acid chain regulator. Byway of example of alpha-omega-aminocarboxylic acids, mention may be madeof aminoundecanoic acid, and by way of example of a lactam mention maybe made of caprolactam and laurolactam, and by way of example ofdicarboxylic acid mention may be made of adipic acid, decanedioic acidand dodecanedioic acid, and by way of example of diamine mention may bemade of hexamethylenediamine. The polyamide blocks are advantageouslycomposed of nylon-12 or of nylon-6. The melting point of these polyamidesequences, which is also that of the copolymer (B), is generally from 10to 15° C. below that of PA 12 or of PA 6.

Depending on the nature of (A), it can be useful to use a copolymer (B)whose melting point is less high in order to avoid degrading (A) duringthe incorporation of (B), and this is the subject of the second andthird embodiment of the invention below.

In a second embodiment of the invention, the polyamide sequences are theresult of condensation of one or more alpha-omega-aminocarboxylic acidsand/or of one or more lactams having from 6 to 12 carbon atoms in thepresence of a dicarboxylic acid having from 4 to 12 carbon atoms, andare of low weight, i.e. {overscore (Mn)} from 400 to 1000. By way ofexample of alpha-omega-amino-carboxylic acid mention may be made ofaminoundecanoic acid and aminododecanoic acid. By way of example ofdicarboxylic acid mention may be made of adipic acid, sebacic acid,isophthalic acid, butanedioic acid, cyclohexane-1,4-dicarboxylic acid,terephthalic acid, the sodium or lithium salt of sulfoisophthalic acid,dimerized fatty acids (these dimerized fatty acids having a dimercontent of at least 98% by weight and preferably being hydrogenated) anddodecanedioic acid HOOC—(CH₂)₁₀—COOH.

By way of example of lactam, mention may be made of caprolactam andlaurolactam.

Caprolactam should be avoided unless the polyamide is purified byremoving the caprolactam monomer which remains dissolved within it.

Polyamide sequences obtained via condensation of laurolactam in thepresence of adipic acid or of dodecanedioic acid and having a weight{overscore (Mn)} of 750 have a melting point of 127-130° C.

In a third embodiment of the invention, the polyamide sequences are theresult of condensation of at least one alpha-omega-aminocarboxylic acid(or one lactam), at least one diamine and at least one dicarboxylicacid. The alpha-omega-aminocarboxylic acid, the lactam and thedicarboxylic acid may be chosen from those mentioned above.

The diamine may be an aliphatic diamine having from 6 to 12 atoms, or itmay be an acrylic and/or saturated cyclic diamine.

By way of examples mention may be made of hexamethylenediamine,piperazine, 1-aminoethylpiperazine, bisaminopropylpiperazine,tetramethylenediamine, octamethylenediamine, decamethylenediamine,dodecamethylenediamine, 1,5-diaminohexane,2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine(IPD), methylpentamethylenediamine (MPDM), bis(amino-cyclohexyl)methane(BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM).

In the second and third embodiment of the invention, the variousconstituents of the polyamide sequence and their proportion are chosenin order to obtain a melting point below 150° C. and advantageouslybetween 90 and 135° C. Low-melting-point copolyamides are described inthe patents U.S. Pat. No. 4,483,975, DE 3 730 504, U.S. Pat. No.5,459,230. The same proportions of the constituents are utilized for thepolyamide blocks of (B). (B) may also be the copolymers described inU.S. Pat. No. 5,489,667.

The polyether blocks may represent from 5 to 85% by weight of (B). Thepolyether blocks may contain units other than the ethylene oxide units,e.g. units of propylene oxide or of polytetrahydrofuran (which leads topolytetramethylene glycol sections within the chain). Simultaneous usemay also be made of PEG blocks, i.e. blocks consisting of ethylene oxideunits, PPG blocks, i.e. blocks consisting of propylene oxide units, andPTMG blocks, i.e. blocks consisting of tetramethylene glycol units, alsotermed polytetrahydrofuran. Use is advantageously made of PEG blocks orof blocks obtained by ethoxylation bisphenols, e.g. bisphenol A. Theselatter products are described in patent EP 613 919. The amount ofpolyether blocks in (B) is advantageously from 10 to 50% by weight of(B) and preferably from 35 to 50%.

The copolymers of the invention may be prepared by any means permittinglinkage of the polyamide blocks to the polyether blocks. Essentially,two processes are used in practice, one being a two-step process and theother being a single-step process.

The two-step process consists firstly in preparing thecarboxylic-terminated polyamide blocks via condensation of precursors ofpolyamide in the presence of a dicarboxylic acid chain regulator, andthen, in a second step, in adding the polyether and a catalyst. If theprecursors of polyamide are only lactams or alpha-omega-aminocarboxylicacids, a dicarboxylic acid is added. If the precursors themselvescomprise a dicarboxylic acid it is used in excess with respect to thestoichiometry of the diamines. The reaction usually takes place between180 and 300° C., preferably from 200 to 260° C., the pressure developingin the reactor being between 5 and 30 bar, and being maintained forabout 2 hours. The pressure is slowly reduced to atmospheric pressureand then the excess water is distilled off, for example for one or twohours.

Once the carboxylic-terminated polyamide has been prepared, thepolyether and a catalyst are then added. The polyether may be added inone or more portions, and the same applies to the catalyst. In oneadvantageous embodiment, the polyether is added first, and the reactionof the terminal OH groups of the polyether and of the terminal COOHgroups of the polyamide begins with formation of ester bonds andelimination of water; water is removed as far as possible from thereaction mixture by distillation, and then the catalyst is introduced inorder to obtain the bond between the amide blocks and the polyetherblocks. This second step is carried out with stirring, preferably undera vacuum of at least 5 mm of Hg (650 Pa) at a temperature such that thereactants and the copolymers obtained are molten. By way of example,this temperature may be between 100 and 400° C. and mostly between 200and 300° C. The reaction is followed by measuring the torque exerted bythe molten polymer on the stirrer or by measuring the electrical powerconsumed by the stirrer. The end of the reaction is determined by thetorque value or target power value. The catalyst is defined as being anymaterial making it easier to bond the polyamide blocks to the polyetherblocks via esterification. The catalyst is advantageously a derivativeof a metal (M) chosen from the group formed by titanium, zirconium andhafnium.

By way of example of a derivative mention may be made of thetetraalkoxides complying with the general formula M(OR)₄, in which Mrepresents titanium, zirconium or hafnium and R, identical or different,indicate linear or branched alkyl radicals having from 1 to 24 carbonatoms.

Examples of the C₁-C₂₄-alkyl radicals among which the radicals R arechosen for the tetraalkoxides used as catalysts in the process accordingto the invention are methyl, ethyl, propyl, isopropyl, butyl,ethylhexyl, decyl, dodecyl, hexadodecyl. The preferred catalysts are thetetraalkoxides for which the radicals R, identical or different, are theC₁-C₈-alkyl radicals. Particular examples of these catalysts areZr(OC₂H₅)₄, Zr(O-isoC₃H₇)₄, Zr(OC₄H₉)₄, Zr(OC₅H₁₁)₄, Zr(OC₆H₁₃)₄,Hf(OC₂H₅)₄, Hf(OC₄H₉)₄, Hf(O-isoC₃H₇)₄.

The catalyst used in the process according to the invention may consistsolely of one or more tetraalkoxides defined above of formula M(OR)₄. Itmay also be formed by combining one or more of these tetraalkoxides withone or more alcoholates of alkali metals or of alkaline earth metalshaving the formula (R₁O)_(p)Y in which R₁ indicates a hydrocarbonradical, advantageously a C₁-C₂₄-alkyl radical, and preferably aC₁-C₈-alkyl radical, Y represents an alkali metal or alkaline earthmetal, and p is the valency of Y. The amounts of alcoholate of alkalimetal or of alkaline earth metal and of tetraalkoxides of zirconium orof hafnium that are combined to constitute the mixed catalyst may varywithin wide limits. However, it is preferable to use amounts ofalcoholate and of tetraalkoxides such that the molar proportion ofalcoholate is approximately equal to the molar proportion oftetraalkoxide.

The proportion by weight of catalyst, i.e. of the tetraalkoxide(s) ifthe catalyst does not include alcoholate of alkali metal or of alkalineearth metal, or else of the entirety of the tetraalkoxide(s) and of thealcoholate(s) of alkali metal or of alkaline earth metal if the catalystis formed by combining these two types of compound, advantageouslyvaries from 0.01 to 5% by weight of the mixture of the dicarboxylicpolyamide with the polyoxyalkylene glycol, and is preferably between0.05 and 2% of that weight.

By way of example of other derivatives, mention may also be made of thesalts of the metal (M), in particular the salts of (M) with an organicacid and the complex salts of the oxide of (M) and/or the hydroxide of(M) with an organic acid. The organic acid may advantageously be formicacid, acetic acid, propionic acid, butyric acid, valeric acid, caproicacid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearicacid, oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylicacid, phenylacetic acid, benzoic acid, salicylic acid, oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid,fumaric acid, phthalic acid and crotonic acid. Acetic and propionicacids are particularly preferred. M is advantageously zirconium. Thesesalts may be termed zirconyl salts. Without being bound by thisexplanation, the Applicant thinks that these salts of zirconium with anorganic acid or the complex salts mentioned above release ZrO⁺⁺ duringthe course of the process. Use is made of the product sold as zirconylacetate. The amount to use is the same as that for the M(OR)₄derivatives.

This process and these catalysts are described in the patents U.S. Pat.No. 4,332,920, U.S. Pat. No. 4,230,838, U.S. Pat. No. 4,331,786, U.S.Pat. No. 4,252,920, JP 07145368A, JP 06287547A and EP 613919.

With respect to the single-step process, all the reactants used in thetwo-step process are mixed, i.e. the precursors of polyamide, thedicarboxylic acid chain regulator, the polyether and the catalyst. Thereactants and the catalyst are the same as those in the two-step processdescribed above. If the precursors of polyamide are only lactams, it isadvantageous to add a little water.

The copolymer essentially has the same polyether blocks and the samepolyamide blocks, but also has a small fraction of the various reactantsrandomly distributed along the polymer chain, having reacted in randomfashion.

The reactor is closed and heated, with stirring, as in the first step ofthe two-step process described above. The pressure that develops isbetween 5 and 30 bar. Once the pressure increase has concluded, reducedpressure is applied to the reactor while maintaining vigorous stirringof the molten reactants. The reaction is followed as above for thetwo-step process.

The catalyst used in this one-step process is preferably a salt of themetal (M) with an organic acid or a complex salt of the oxide of (M)and/or the hydroxide of (M) with an organic acid.

The ingredient (B) may also be a polyetheresteramide (B) havingpolyamide blocks comprising sulfonates of dicarboxylic acids either aschain regulators for the polyamide block or in association with adiamine as one of the monomers constituting the polyamide block, andhaving polyether blocks essentially consisting of alkylene oxide units,as described in the international application PCT/FR00/02889.

The compatibilizer C is a block copolymer comprising at least onepolymerized block comprising styrene and at least one polymerized blockcomprising ethylene oxide units.

The polymerized block comprising styrene is generally present in C in aproportion of from 60 to 99% by weight and preferably from 60 to 98% byweight.

The polymerized block comprising ethylene oxide units is generallypresent in C in a proportion of from 40 to 1% by weight and preferablyfrom 40 to 2% by weight.

The polymerized block comprising styrene generally has a glasstransition temperature above 100° C. and preferably comprises at least50% by weight of styrene. The polymerized block comprising styrene mayalso comprise an unsaturated epoxide (obtained by copolymerization),this latter preferably being glycidyl methacrylate. The unsaturatedepoxide may be present in a proportion of from 0.01% to 5% by weight inthe polymerized block comprising styrene.

The block copolymer comprising at least one polymerized block comprisingstyrene and at least one polymerized block comprising ethylene oxideunits may also be grafted with an unsaturated epoxide, preferablyglycidyl methacrylate.

By way of example of unsaturated epoxide, mention may be made of:

-   -   the aliphatic glycidyl esters and aliphatic glycidyl ethers,        such as allyl glycidyl ether, vinyl glycidyl ether, glycidyl        maleate and glycidyl itaconate, and glycidyl(meth)acrylate, and    -   the alicyclic glycidyl esters and alicyclic glycidyl ethers,        such as 2-cyclohexene glycidyl ether, diglycidyl        cylohexene-4,5-dicarboxylate, glycidyl        cyclohexene-4-carboxylate, glycidyl        2-methyl-5-norbornene-2-carboxylate and diglycidyl        cis-endo-bicyclo[2.2.1]-5-heptene-2,3-dicarboxylate.

In the block comprising styrene, part of the styrene may be replaced byunsaturated monomers copolymerizable with styrene, and by way of examplemention may be made of alpha-methylstyrene and the (meth)acrylic esters.In this case, the block comprising styrene is a copolymer of styrene,among which mention may be made of styrene-alpha-methylstyrenecopolymers, styrene-chlorostyrene copolymers, styrene-butadienecopolymers, styrene-isoprene copolymers, styrene-vinyl chloridecopolymers, styrene-vinyl acetate copolymers, styrene-alkyl acrylatecopolymers (methyl acrylate, ethyl acrylate, butyl acrylate, octylacrylate, phenyl acrylate), styrene-alkyl methacrylate copolymers(methyl methacrylate, ethyl methacrylate, butyl methacrylate, phenylmethacrylate), styrene-methyl chloroacrylate copolymers andstyrene-acrylonitrile-alkyl acrylate copolymers.

The polymerized block comprising ethylene oxide units preferablycomprises no comonomer. This block generally terminates in the function—OH deriving from the ethylene glycol used as monomer for itspreparation.

In particular, C may be:

-   -   a diblock copolymer comprising a block of a polymer of styrene        and a block of a polymer of ethylene glycol (polyethylene        glycol);    -   a diblock copolymer comprising a homopolystyrene block and a        block of a polymer of ethylene glycol (polyethylene glycol);        Within the scope of the invention is it possible to use one or        more compatibilizers C.

The compatibilizer C may in particular be prepared by controlledfree-radical polymerization methods in the presence of a stable freeradical (generally a nitroxide) following the principle of the teachingof WO 9411412 or WO 96/24260 or EP 927727.

The level of antistatic properties increases with the proportion of (B)and, for equal amounts of (B), with the proportion of ethylene oxideunits present in (B).

According to the application, preference will be given to including aproportion of (B) sufficient to obtain, in the final composition, asurface resistivity below 5.10¹³ ?/? measured to the standard IEC93.According to the application, preference will be given to including aproportion of (B) sufficient to give the final composition a volumeresistivity below 5.10¹⁶ ?.cm measured to the standard IEC93.

The amount of (B)+(C) is advantageously from 5 to 30 parts per 95-70parts of (A) and preferably from 10 to 20 per 90-80 parts of (A). The(B)/(C) ratio is advantageously between 4 and 10. The amount of C in thecomposition may be from 0.5 to 5 parts by weight per 100 parts by weightof composition.

Within the scope of the invention it is possible to add mineral fillers(talc, CaCO₃, kaolin, etc.), reinforcing agents (glass fiber, mineralfiber, carbon fiber, etc.), stabilizers (heat, UV), flame retardants andcolorants.

The compositions of the invention are prepared by the methods usual forthermoplastics, e.g. by extrusion or with the aid of twin-screw mixers.

The present invention also provides the articles manufactured with thepreceding compositions; examples of these are films, pipes, sheets,packaging, cases for computers, for fax machines or for telephones.

A method of preparing a PS-b-PEG block copolymer is given below.

Materials Used:

-   -   HO-TEMPO (or TEMPO-OH):        4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy usually marketed        as 4-hydroxy TEMPO;    -   Azocarboxy: 4,4′-azobis(cyanovaleric acid):    -    (this product is marketed by ATOFINA with the name        “azocarboxy”)    -   POE: poly(ethylene glycol)methyl ether:        -   CH₃—(O—CH₂—CH₂)₄₅—OH    -   DCC: dicylcohexylcarbodiimide:    -   DMAP: dimethylaminopyridine:

The synthesis is conducted in two steps:

-   1. Synthesis of the AZO-PEG macroinitiator, then-   2. (Controlled) free-radical polymerization of styrene    1. Synthesis of the AZO-PEG Macroinitiator

The table below brings together the ingredients and the quantities usedfor this synthesis: AZO g 2.832 mol 0.0101 POE-OH g 44.75 mol 0.0224 DCCg 4.13 mol 0.0200 DMAP g 0.145 mol 0.0012 CH₂Cl₂ g 141.5 mol 1.656 THF g86.5 mol 1.196

The solid compounds (POE-OH, azocarboxy and DMAP) are weighed, mixed andintroduced into a 1 l glass reactor. The solvents are then added (firstdichloromethane to dissolve the POE-OH then the THF to dissolve theazocarboxy) and cooled to a temperature of 0° C. The DCC is introducedwith the aid of a syringe and a needle (being in solution in thedichloromethane) through a septum. The reaction is carried out at 0° C.for one hour, and the mixture is allowed to stand at ambient temperaturefor 20 hours (with mechanical stirring). The product is thenBuchner-filtered: the filtrate is collected and the solvents (THF andCH₂Cl₂) are evaporated (rotary evaporator at ambient temperature). Theresidue is then dissolved in CH₂Cl₂, and Buchner filtered. The filtrateis evaporated again (rotary evaporator at ambient temperature) and theproduct is dried in a drying cabinet at ambient temperature for 12 h(yield 74%).

Analysis by C13 NMR: Yield by Free POE- POE-AZO- POE-AZO Mn (POE) weight(%) OH (%) POE (%) (%) (g/mol) Time 74 16.2 83.8 0 1823 ≧20 h

These results are determined by C13 NMR analysis. The initiatorcomprises 83.3% of 4,4′-azobis(polyethylene glycol cyanovalerate) and16.2% of unreacted PEG-OH.

2. Controlled Free-Radical Polymerization TEMPO-OH STYRENE WeightConcentration INITIATOR (g) (g) (mol/l) (g) 802 1.381 0.00908 16.98

The TEMPO-OH is dissolved in the styrene and then introduced into aflask containing the initiator from step 1. The flask is degassed bybubbling nitrogen for about 20 min. The flask is then placed in an oilbath preheated to about 140° C. The polymerization is conducted for 720min and samples for following the kinetics are regularly taken. The timezero corresponds to achievement of a temperature of 100° C. of thereaction mixture. At the end of the synthesis, the product isprecipitated in methanol, filtered and dried in vacuo at 50° C. for 12h.

Results:

The analyses were conducted in THF at ambient temperature. Time (min) Mw(g/mol) Mn (g/mol) Ip Conversion (%) 186 29 700 24 400 1.2 22.07 387 41500 33 100 1.3 37.62 480 47 000 36 450 1.3 46.54 720 (final) 64 700 50600 1.3 87.14

The samples were analyzed at 50° C. in deuterated chloroform, using ¹HNMR: we determine the PS/PEG ratio by weight and the content by weightof monomeric styrene, based on the polymer, by integrating theunresolved complex peak for the PS aromatic protons (deducting thecontribution from the monomeric styrene), integrating the narrow peaksof the CH2= group of the monomeric styrene and integrating the narrowpeak of the ether groups of the PEG.

To gain an idea of the composition by weight, we used the Mn valuesdetermined by GPC and deduced a PS/PEG ratio by weight assuming the Mnof the PEG to be 2000 g/mol. The GPC results and the NMR results are ingood agreement. % by weight PS-b-PEG Ratio PS/PEG NMR 97%/3% RatioPS/PEG GPC 96%/4%

1. A composition comprising, per 100 parts by weight: from 99 to 60parts by weight of a styrenic polymer (A), from 1 to 40 parts by weightof (B)+(C), (B) being a copolymer containing polyamide blocks andpolyether blocks comprising ethylene oxide units —C₂H₄O)—, and (C) beinga compatibilizer selected from block copolymers comprising at least onepolymerized block comprising styrene and at least one polymerized blockcomprising ethylene oxide units, the (B)/(C) ratio by weight beingbetween 2 and
 10. 2. The composition as claimed in claim 1 wherein theproportion of (B) is sufficient to give the final composition a surfaceresistivity below 5.10^(13 Ω/□) measured to the standard IEC93.
 3. Thecomposition as claimed in claim 1 wherein the proportion of (B) issufficient to give the final composition a volume resistivity below5.10^(16 Ω)·cm measured to the standard IEC93.
 4. The composition asclaimed in claim 1, wherein the (B)/(C) ratio is between 4 and
 10. 5.The composition as claimed in claim 1, wherein (A) comprises more than50% of styrene.
 6. The composition as claimed in claim 1, wherein theamount of (C) is from 0.5 to 5 parts by weight in 100 parts by weight ofsaid composition.
 7. The composition as claimed in claim 1, wherein thepolymerized block comprising styrene is present in C in a proportion offrom 60 to 99% by weight and wherein the polymerized block comprisingethylene oxide units is present in C in a proportion of from 40 to 1% byweight.
 8. The composition as claimed in claim 1, wherein thepolymerized block comprising styrene is present in C in a proportion offrom 60 to 98% by weight and wherein the polymerized block comprisingethylene oxide units is present in C in a proportion of from 40 to 2% byweight.
 9. The composition as claimed in claim 1, wherein thepolymerized block comprising styrene comprises at least 50% by weight ofstyrene.
 10. The composition as claimed in claim 1, wherein thepolymerized block comprising styrene comprises glycidyl methacrylate.11. The composition as claimed in claim 1, wherein the polymerized blockcomprising ethylene oxide units comprises no comonomer.
 12. Thecomposition as claimed in claim 1, wherein the block copolymercomprising at least one polymerized block comprising styrene and atleast one polymerized block comprising ethylene oxide units is graftedwith glycidyl methacrylate.
 13. The composition as claimed in claim 1,wherein (A) is a styrene-butadiene copolymer.